1. Field of the Invention
This invention relates to digital recording apparatuses used in conjunction with television and video cameras for observation, monitoring and security applications.
2. Description of the Prior Art
Signals of television cameras used in an observation system are fed to the monitoring site via closed wired circuits, or via public communication lines such as analog telephone lines or digital telephone lines, or via computer network or via RF links are commonly recorded onto a video cassette, such as the well known VHS, using VHS recorder. The VHS recorder is an analog recorder for recording analog television signals. Such analog recording onto VHS cassettes have been accepted by the courts at large as evidence, primarily on the grounds that the altering of the signals content is extremely difficult and moreover, such tampering with the recorded signals by trying to alter its content can be detected by experts. Moreover, the wide use of such analog recording onto VHS cassettes made the analog recording low in cost and popular. With the recent advances in digital recording of television signals it became simple to record the signal of television cameras used in observation system onto a hard disk of a PC or onto a hard disk of a specially constructed digital recorders. However, the hard disk of the PC or of the digital recorder has a finite capacity, which limits the length of time for archiving and/or storing the accumulated recorded signals. This can be solved by adding multiple hard disks or by using retractable hard disks. However, such retractable hard disk is very costly and requires expertise in handling. Another method to archive and store the recorded digital signals is by transferring the recorded digital signals onto digital tapes, cassettes, diskettes or disks such as the well-known CD or DVD.
This however causes a serious legal problem, hindering the use of the recorded material in courts; first because the recording is no longer the original recorded media, and secondly, it is literally impossible to identify the original from a copied or transferred data, and thirdly it is simple to alter a digitally recorded picture by changing its color, changing its time and date, removing objects from the picture content or adding objects into the picture. The ability to present a modified picture and to present a copied recording as an original recording, prevents the use of the digitally recorded pictures on tape, disk or diskette as evidence in courts. Furthermore, the tapes, disks and diskettes offer a limited recording time for no more than several hours which requires constant attendance for unloading and loading the tapes, disks and the diskettes, alternatively there are variety of automatic machines known as “juke boxes” for loading, unloading the recorded media that also provide for management of the recorded data. Such juke boxes however have also a finite data storage capacity and are very costly.